1. Field of the Invention
The present invention relates to a radiation detecting element, a radiographic image detecting panel and a radiographic image detecting apparatus. The present invention particularly relates to a radiation detecting element, a radiographic image detecting panel and a radiographic image detecting apparatus that directly convert radiation into charges.
2. Description of the Related Art
Recently, in most radiographic image detecting apparatuses, a FPD (flat panel detector) that has an X-ray sensitive layer disposed on a TFT (Thin Film Transistor) active matrix substrate and is capable of directly converting X-ray information into digital data, is employed as a radiation detecting element. Making a smaller pixel size is effective in raising the resolution of a FPD. Particularly, in a direct-conversion-type radiation detecting element that employs selenium (Se) in a photoelectric conversion layer for absorbing radiation and converting into charges, the pixel size contributes to raising the resolution. Accordingly, there have recently been attempts to raise the quality by high miniaturization of the pixel size.
However, in a FPD, the charge amount capable of being collected reduces in proportion to the reduction in pixel size, and as a result the sensitivity (S/N) is lowered, such that sometimes even though the resolution is raised, overall quality DQE actually drops. Accordingly, there is a proposal that attempts to achieve a higher light utilization ratio whilst raising resolution and maintaining S/N by arraying pixels with a hexagonal shaped profile in a honeycomb pattern (see for example Japanese Patent Application Laid-Open (JP-A) No. 2003-255049 and JP-A No. 2000-105278).
An apparatus described in JP-A No. 2003-255049 is an indirect-conversion-type radiation detecting apparatus that is not equipped with capacitors (auxiliary capacitors) to accumulate charges obtained by photoelectric conversion. Common ground lines such as those in a direct-conversion-type radiographic image detecting apparatus are accordingly not required. Thus bias lines 103 illustrated in FIG. 9 of JP-A No. 2003-255049 are wiring in an upper portion of the photoelectric conversion section, and design degrees of freedom are secured for the bias lines. However, the auxiliary capacitors mentioned above are required for direct-conversion-type radiographic image detecting apparatuses, and so bias lines need to be placed. In a radiation detecting section of a direct-conversion-type radiographic image detecting apparatus, a case is illustrated in FIG. 7 in which hexagonal shaped pixels are arrayed in a honeycomb pattern and the position of TFT switches 204 within the pixels is, similarly to in cases of rectangular pixel shape, placed so as to face in the same direction for all the pixels, with common ground lines 203 snaking to match the data lines 201 so that the data lines 201 do not intersect with the common ground lines 203. In such cases, locations arise where the distance to the TFT switches becomes narrower, at portions where the common ground lines 203 snake to the left or right (see the portions encircled in intermittent lines in FIG. 7. In FIG. 7 the distance to the TFT switches gets nearer at the portions where snaking to the left). Moreover, due to the distance between the TFT switches and the data lines becoming narrow, the common ground lines 203 touch the TFT switches, making it difficult to layout the common ground lines. Moreover, the resistance of the lines rises in cases in which there are narrower common ground lines 203, making it difficult to maintain the common voltage (ground).
Moreover, in cases in which the data lines 201 and the common ground lines 203 approach each other, the capacitance between the data lines and the common ground lines increases. This is consequently a significant impediment to high degrees of miniaturization of pixels of a radiation detecting element, and means that the resolution of the radiation detecting element cannot be raised.
The present invention provides a radiation detecting element, a radiographic image detecting panel and a radiographic image detecting apparatus that achieve greater miniaturization whilst avoiding the interline pitch of signal lines becoming narrower.